Is this a A50 or A65?

[hedgehorn]

I am trying to figure out if this bike is a A50 or A65. I was told when I bought it that it was a A65 but A50 is stamped on the left side of the case just below the cylinder and the serial # is A502 688. Please help. Thanks,
                                                 Todd
Also everytime I have tried to add a photo I get an error message that the file name already exists on the server. I have tried naming it many different times and have had no success. What am I doing wrong?

[L.A.B.]

Todd,
The crankcases would appear to be A50 items!
http://www.bsaoc.demon.co.uk/post1960.html
BUT... this could mean a number of things.

The bike may have been originally built as an A65 but at some point A50 crankcases or more parts have been fitted?
 (a large number of parts are common to both models - including the crankcases)
Or:
It's an A50!
Or:
The bike was originally built as an A50 and later converted to A65 spec?
(would technically still be an A50 I suppose?)


Are you sure that the '2' = (A502) isn't a letter rather than a number?
What is the frame number prefix? Later A65 frame numbers had A65 prefix, any idea of the year?

If you email your photo direct to Nigel I'm sure he can post it up for you?

[hedgehorn]

I am thinking it is an A50 the A502 is the actual serial on the title I will take a look at the frame numbers. Are there any other differences that one might note?

[L.A.B.]

Are there any other differences that one might note?

A50 and A65 are basically identical machines apart from cylinder head, carb/s, (what carb/s is/are fitted?) barrel and pistons, gearing and possibly wheels?  etc.
Checking through a parts book seems to show that about 95% of parts are the same for both models, some wheel part numbers are different but without knowing the exact year I cannot be more precise.

You could remove the cylinder head and measure the bores?

[hedgehorn]

The serial on the frame reads A50.2688. It has one amal monobloc carb. A 17 tooth front  and a 42 tooth rear Chainwheel. The exact year is a 1963. I apreciate all your help. I will be taking the engine apart soon to inspect parts and clear the sludge trap.      
                                         Todd

[L.A.B.]

17 tooth front sprocket would have been the original part for A50 ( A65 = 20 tooth).
Rear sprocket is the same for both.

A50 carb = 376/
A65 carb = 389/

[hedgehorn]

Does your book say what size the front wheel should be on the A50 mine is fitted with a 3.5-18 tire and a 400-18 on the rear. Most other brittish bikes I have looket at have a 19'' front wheel. Thanx again for your assistance
                                                                      Todd

[L.A.B.]

There are some differences in wheel sizes according to the models and years but 18" front/18" rear is probably correct, most later models did have 19" wheels.
The A50 front brake parts do seem to be different to A65 though?

-------------------------------------------------------

Further research shows that the '63 A50 had a 7" diameter front drum brake, (A65 = 8").

[VintageBike]

Here is a link to the picture of the bike...
http://www.vintagebike.co.uk/YaBBAttach/rustya50.jpg

[hedgehorn]

Thanks very much for all your help on this matter I now need to find a good repair manual for a 63' A50. If the factory one cant be found what is the best to buy?
                                                             Todd

[L.A.B.]

Factory manual and parts book copies (and other BSA books) UK:
http://brucemain-smith.com/frames.html>Photocopies =B>Manufacturer = BSA>Date Range = 1958 - 1967.

Haynes manual:
http://www.motolit.com/bsatwina50a6.html

Clymer manual:
http://www.themotorbookstore.com/vinbritstree.html

[Welsh_Wizard]

These Details from the 1465/63 Get Away with BSA export listing
500 Star
Bore 65.5
stroke 74
CC 499
compression 8.5
Transmission sprockets
engine 17
clutch 58
gearbox solo 17
gearbox sidecar 16
rear wheel solo 42
rear wheel sidecar 43
topgear 5.11
third 5.85
second 8.18
first 12.82
chain front 3/8 triple
chain rear 5/8 x 3/8
brakes
front 7"
rear 7"
Tyres
front 3.25 - 18
rear 3.50 - 18

Hope these are of use
WW